This invention relates to an improved method and composition for cleaning rusted metal surfaces and, more particularly, to an aqueous solution of a water-soluble polymer and a chelating agent, which forms a hard encapsulating film upon application to the metal surface to be cleaned and, after cleaning, is easily peeled away and disposed of.
The prior art has attempted to clean metal surfaces and, in particular, iron-based surfaces containing "rust", i.e., iron oxides such as Fe.sub.3 O.sub.4 and Fe.sub.2 O.sub.3, by the use of various acidic cleaning solutions. Chemicals such as inhibited hydrochloric acid, ethylenediaminetetraacetic acid (EDTA), EDTA/citric acid, and the like have been used to clean metal surfaces having rust and other scale-like deposits. Although very thin polymeric films have been used as long-lasting corrosion-inhibiting films on metal surfaces, they have not been used as a rust cleaner.
One particularly difficult type of metal surface to clean is the irregular surfaces found on ships, i.e., high-temperature valves, pipes, and the like. Frequently, the only cleaning method feasible is the lengthy and tiresome process of wire brushing the surface to be cleaned and then subsequently applying a solution of a wetting agent mixed with a cleaning agent to the metal surface. Such a technique suffers from the difficulty of keeping the cleaning fluid in contact with the surface to be cleaned, such as overhead objects, as well as the subsequent disposal of liquid wastes. Additionally, these solutions are often toxic, non-economical, and require large volumes of water for washing purposes.